Update textbook.fr.md

12.temporary_ins/96.electromagnetism-in-media/20.reflexion-refraction-at-interfaces/20.metallic-waveguides/10.main/textbook.fr.md

@@ -27,12 +27,15 @@ _TE and TM waves and their corresponding standing wave behaviour along the y axi
 $`\overrightarrow{E}_{\perp}=`$$`\underbrace{-2\,E_0\,\sin(k\cdot y\cdot \cos\theta)}_{\large{amplitude}}
 \times \sin\big(\underbrace{k\,\sin\theta}_{\large{wavevector}} z-\omega t\big)\overrightarrow{e_z}`$    
 
+$`\overrightarrow{E}_{\perp}=`$$`\underbrace{-2\,E_0\,\sin(k\, y\, \cos\theta)}_{\large{amplitude}}
+\times \sin\big(\underbrace{k\,\sin\theta}_{\large{wavevector}} z-\omega t\big)\overrightarrow{e_z}`$    
+
    
 $`\overrightarrow{B}_{\perp}=`$
 $`\left(\begin{array}{l}
 0\\
--\dfrac{2\,E_0}{c}\sin\theta \,\sin\,(k\cdot y \cdot \cos\theta)\,\sin\,(k\,\sin\theta\,z -\omega t)\\
--\dfrac{2\,E_0}{c}\cos\,\theta \,\cos\,(k\cdot y \cdot \cos\,\theta)\,\cos\,(k\,\sin\theta\,z -\omega t)
+-\dfrac{2\,E_0}{c}\sin\theta \cdot \sin\,(k\, y \, \cos\theta)\times \sin\,(k\,\sin\theta\,z -\omega t)\\
+-\dfrac{2\,E_0}{c}\cos\,\theta \cdot\cos\,(k\cdot y \cdot \cos\,\theta)\times\cos\,(k\,\sin\theta\,z -\omega t)
 \end{array}\right)`$
 
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